Efficient Computation of Nonparaxial Surface Fields Excited on an Electrically Large Circular Cylinder with an Impedance Boundary Condition

Cataloged from PDF version of article.An alternative numerical approach is presented for the evaluation of the Fock-type integrals that exist in the uniform geometrical theory of diffraction (UTD)-based asymptotic solution for the nonparaxial surface fields excited by a magnetic or an electric source located on the surface of an electrically large circular cylinder with an impedance boundary condition (IBC). This alternative approach is based on performing numerical integration of the Fock-type integrals on a deformed path on which the integrands are nonoscillatory and rapidly decaying. Comparison of this approach with the previously developed one presented in [1], which is based on invoking the Cauchy’s residue theorem by finding the pole singularities numerically, reveals that the alternative approach is considerably more efficient

Value creation by Turkish enterprises

This study focuses on the resurgence of the automotive and appliance sectors in Turkey’s recent years. The analysis of both these sectors reveals some interesting lessons about technology management and investment strategies for companies to invest in Turkey. We discuss the major changes and project the future in both industries. Turkey seems to be a clear winner though there are some factors that could reverse the trend. The research is a joint field study partne rship between Carnegie Mellon and Sabanci Universities

Scattering from an Impedance Object at the Edge of a Perfectly Conducting Wedge

Cataloged from PDF version of article.In this study, scattering from impedance bodies positioned at the edge of a perfectly electrically conducting wedge is investigated. In the treatment of the problem, eigenfunction expansion in terms of spherical vector wave functions is employed. A complete dyadic Green's function for the spherical impedance boss at the edge is developed. It is observed that the scattering is highly enhanced by the edge guided waves. Additionally, using T-matrix method, the solution is extended to the general case of irregularly shaped scatterers. The T-matrix solution is verified by applying it to the case of a spherical scatterer and results are compared with the dyadic Green's function solution. © 2013 IEEE

Physical optics modeling of 2D dielectric lenses

Cataloged from PDF version of article.We propose an advanced physical optics formulation for the accurate modeling of dielectric lenses used in quasi-optical systems of millimeter, submillimeter, and infrared wave applications. For comparison, we obtain an exact full-wave solution of a two-dimensional lens problem and use it as a benchmark for testing and validation of asymptotic models being considered. © 2009 Optical Society of Americ

Closed-Form Green's Function Representations in Cylindrically Stratified Media for Method of Moments Applications

Cataloged from PDF version of article.Closed-form Green's function (CFGF) representations for cylindrically stratified media, which can be used as the kernel of an electric field integral equation, are developed. The developed CFGF representations can safely be used in a method of moments solution procedure, as they are valid for almost all possible source and field points that lie on the same radial distance from the axis of the cylinder (such as the air-dielectric and dielectric-dielectric interfaces) including the axial line (ρ = ρ′ and φ = φ′), which has not been available before. In the course of obtaining these expressions, the conventional spectral domain Green's function representations are rewritten in a different form so that i) we can attack the axial line problem and ii) the method can handle electrically large cylinders. Available acceleration techniques that exist in the literature are implemented to perform the summation over the cylindrical eigenmodes efficiently. Lastly, the resulting expressions are transformed to the spatial domain using the discrete complex image method with the help of the generalized pencil of function method, where a modified two-level approach is used. Numerical results are presented in the form of mutual coupling between two current modes to assess the accuracy of the final spatial domain CFGF representations. © 2009 IEE

Complex source radiation in a cylindrical radome of metal-dielectric grating

Cataloged from PDF version of article.The radiation fields of a line source enclosed in a circular dielectric radome with grating consisting of an array of thin lossy metal strips are analyzed. The variations of the directivity of the source beam with respect to the beam direction are studied. The possibility of damping these variations by an appropriate design of the radome is demonstrated

Dynamics of Entanglement and Bell-nonlocality for Two Stochastic Qubits with Dipole-Dipole Interaction

We have studied the analytical dynamics of Bell nonlocality as measured by CHSH inequality and entanglement as measured by concurrence for two noisy qubits that have dipole-dipole interaction. The nonlocal entanglement created by the dipole-dipole interaction is found to be protected from sudden death for certain initial states

Examination of Existent Propagation Models Over Large Inhomogeneous Terrain Profiles Using Fast Integral Equation Solution

Cataloged from PDF version of article.The accuracyof most widelyused empirical models are investigated using the spectrallyaccelerated forward-backward (FBSA) method as a benchmark solution. First, FBSA results are obtained for propagation over large scale terrain profiles and compared with measurements to assess the accuracyof FBSA. Then, accuracyof some International Telecommunication Union (ITU) and Federal Communications Commission (FCC) propagation models are investigated. It has been observed that, for rural areas, the prediction of the most recent ITU recommended propagation model (Rec. 1546) deviates much more than older models do

Numerical optimization of a cylindrical reflector-in-radome antenna system

Cataloged from PDF version of article.Accurate numerical optimization based on the rigorous solution of the integral equation using the method of analytical regularization is performed for the cylindrical reflector antenna in a dielectric radome. It is shown that the multiple scattering in this system is more significant for the optimum radome design than any nonplane-wave effects or the curvature of the radome. We claim that, although the common half-wavelength design is a good approximation to avoid negative effects of the radome (such as the loss of the antenna directivity), one can, by carefully playing with the radome thickness, its radius, reflector location, and the position of the feed, improve the reflector-inradome antenna performance (e.g., increase the directivity) with respect to the same reflector in free-space

Characteristic Basis Function Method for Solving Electromagnetic Scattering Problems over Rough Terrain Profiles

Cataloged from PDF version of article.A computationally efficient algorithm, which combines the characteristic basis function method (CBFM), the physical optics (PO) approach (when applicable) with the forward backward method (FBM), is applied for the investigation of electromagnetic scattering from—and propagation over—large-scale rough terrain problems. The algorithm utilizes high-level basis functions defined on macro-domains (blocks), called the characteristic basis functions (CBFs) that are constructed by aggregating low-level basis functions (i.e., conventional sub-domain basis functions). The FBM as well as the PO approach (when applicable) are used to construct the aforementioned CBFs. The conventional CBFM is slightly modified to handle large-terrain problems, and is further embellished by accelerating it, as well as reducing its storage requirements, via the use of an extrapolation procedure. Numerical results for the total fields, as well as for the path loss are presented and compared with either measured or previously published reference solutions to assess the efficiency and accuracy of the algorithm